What if the bearing has a surface layer – for example a whitemetal faced thrust bearing?
A9. The interface between the substrate and the surface layer will also reflect ultrasound. It is important to separate this reflection from the oil film reflection. In most cases this is straightforward, but occasionally the layer thickness is such that it overlaps with the required reflection – in this case some special signal processing is needed. We have tested many kinds of whitemetal faced journal and thrust bearings and these present no problem. A case hardened layer will not cause any significant reflection.
